The present invention relates to a thin-film magnetic head with a magnetoresistive effect element (MR element) such as a giant magnetoresistive effect element (GMR element) using for example a spin-valve (SV) magnetoresistive effect, and a tunnel magnetoresistive effect element (TMR element). Also, the present invention relates to a head suspension assembly (HSA) with the thin-film magnetic head, to a magnetic disk device with the HSA and to a manufacturing method of them.
In a magnetic recording device such as a magnetic disk device, a thin-film magnetic head provided with an anisotropic magnetoresistive effect element (AMR element) made of magnetoresistance material having a resistance that changes depending upon the variation of applied external magnetic field is widely adopted. NiFe alloy (permalloy) has been used as the magnetic material of the AMR element.
Recently, the demand for miniaturization and larger data storage capacity of a magnetic recording medium has become remarkable. Hence, utilization of a GMR element which provides more powerful magnetoresistive effect is advancing quickly and development of a TMR element is also progressing abruptly.
The most popular GMR element is a SVMR element with a SV multi-layered film which has two ferromagnetic material layers separated by a nonmagnetic material layer. Magnetization direction of one of the ferromagnetic layers is constrained or maintained by an exchange coupling and that of the other is free to rotate in response to externally applied magnetic field. A large magnetoresistive effect can be obtained due to the change in the relative difference between the magnetization directions of these two ferromagnetic material layers. Since such GMR element can saturate its magnetization at a lower magnetic field than the AMR element, it is possible to read high density magnetic information.
In order to satisfy the demand for miniaturization and larger data storage capacity, the magnetic materials used for the thin-film magnetic head have been changed and also the structure of the thin-film magnetic head has been downsized. Most typical example of the downsizing is to reduce the thickness of each layer of the read element and the write element in the magnetic head.
The thin-film magnetic head with the GMR element or the TMR element is fabricated by the thin-film multi-layering process and thus each layer thereof tends to become extremely thicker. The GMR multi-layered film is in general sandwiched by two magnetic shield layers called as lower and upper shield layers. Insulation layers called as lower and upper shield gap layers for ensuring electrical insulation of the GMR film are formed between this element and the lower and upper shield layers, respectively.
As aforementioned, these lower and upper shield gap layers are extremely thinned in order to meet the needs of the recent downsizing over the GMR element. For example, the thickness of the shield gap layer in the AMR element is 100 nm or more, whereas that of the GMR element is about 50-60 nm which is substantially half as that of the AMR element. It is considered that these shield gap layers will be more thinned in the future.
Such thinner lower and upper shield gap layers may invite a damage of the thin-film magnetic head due to electro-static discharge (ESD). Electric charges staying on the surfaces of a human body and an object are called as static electricity, and a damage produced in an electronic element by the movement of the electric charge when the human body and the object contact and break with each other is called as an ESD damage. The ESD damage occurring when the element contacts with a charged member can be prevented to some extent by properly selecting the material of the member and by performing the antistatic processing of the element. However, if the worker himself is charged, it is difficult to prevent the ESD damage of the electronic element.
If a man performs a certain action, static electricity will arise on the human body. Although the electro-static voltage of the human body goes up and down according to humidity environment, easy operation such as for example walking on a carpet makes on the human body high electro-static voltage of about 35000 V under the atmosphere of a relative humidity of 10 per cent. If the floor is made of vinyl, the electro-static voltage of about 12000 V arises under the same atmosphere.
Resistance properties against ESD of various electronic devices used widely now are clarified through many researches. If 300-2500 V is applied to a simple transistor, 50-1000 V to a CMOS with a protection circuit, 10-100 V to a MOS-FET and only 5-10 V to the conventional general MR head, breakdown will occur. In case of the GMR element downsized, breakdown will occur at a lower electro-static voltage than that of the AMR head.
It should be noted that, in the GMR element or the TMR element, not only the breakdown may occur due to ESD but also the pinned or fixed direction of magnetization in the ferromagnetic material layer may change due to a little ESD.
It is therefore an object of the present invention to provide a thin-film magnetic head, a HSA with the thin-film magnetic head, a magnetic disk device with the HSA and a manufacturing method of them, whereby improved resistance properties against ESD can be obtained during fabrication.
A thin-film magnetic head, a HSA with the thin-film magnetic head and a magnetic disk device with at least one HSA has insulation layers. Particularly, according to the present invention, at least a part of the insulation layers is made of an insulation material which increases electric conductivity thereof when an ultraviolet radiation is irradiated.
All or a part of the insulation layers in the thin-film magnetic head are made of an insulation material that increases its electric conductivity when an ultraviolet radiation is irradiated, namely that has a photoconduction effect (internal photoelectric effect) to the ultraviolet radiation. Thus, if the thin-film magnetic head with the MR element, the HSA or the magnetic disk device is handled under the ultraviolet radiation irradiated environment, it is possible to reduce the resistance of the insulation layer only during the handling. Thus, various problems due to ESD, such as the ESD damage or the undesirable rotation of the pinned direction in the MR element can be prevented from occurring.
It is preferred that the thin-film magnetic head includes an element formed surface on which at least one head element is formed, and that the at least a part of the insulation layers includes an overcoat layer for covering the element formed surface.
It is also preferred that the thin-film magnetic head includes a MR element having shield gap layers, a MR film sandwiched by the shield gap layers and lead conductors connected to the MR film and sandwiched by the shield gap layers, and that the at least a part of the insulation layers includes the shield gap layers.
Preferably, the MR element is a GMR element or a TMR element.
It is preferred that the at least a part of the insulation layers includes a GaN film. More preferably, the at least a part of the insulation layers includes an under layer of an AlN film, and a GaN film deposited on the AlN film.
According to the present invention, also, a method of manufacturing a thin-film magnetic head includes a step of forming at least a part of insulation layers of the thin-film magnetic head with an insulation material which increases electric conductivity thereof when an ultraviolet radiation is irradiated, and a step of performing at least a part of subsequent processes by irradiating an ultraviolet radiation to the thin-film magnetic head.
Furthermore, according to the present invention, a method of manufacturing a HSA with a thin-film magnetic head includes a step of forming at least a part of insulation layers of the thin-film magnetic head with an insulation material which increases electric conductivity thereof when an ultraviolet radiation is irradiated, and a step of performing at least a part of subsequent processes by irradiating an ultraviolet radiation to the thin-film magnetic head.
According to the present invention, in addition, a method of manufacturing a magnetic disk device with a thin-film magnetic head includes a step of forming at least a part of insulation layers of the thin-film magnetic head with an insulation material which increases electric conductivity thereof when an ultraviolet radiation is irradiated, and a step of performing at least a part of subsequent processes by irradiating an ultraviolet radiation to the thin-film magnetic head.
If the thin-film magnetic head with the MR element, the HSA or the magnetic disk device is handled under the ultraviolet radiation irradiated environment as aforementioned, it is possible to reduce the resistance of the insulation layer during the handling. Thus, various problems due to ESD, such as the ESD damage or the undesirable rotation of the pinned direction in the MR element can be prevented from occurring.
It is preferred that the thin-film magnetic head includes an element formed surface on which at least one head element is formed, and that the forming step includes forming an overcoat layer for covering the element formed surface with an insulation material which increases electric conductivity thereof when the ultraviolet radiation is irradiated.
It is also preferred that the thin-film magnetic head includes a MR element having shield gap layers, a MR film sandwiched by the shield gap layers and lead conductors connected to the MR film and sandwiched by the shield gap layers, and that the forming step includes forming the shield gap layers with an insulation material which increases electric conductivity thereof when the ultraviolet radiation is irradiated.
Preferably, the MR element is a GMR element or a TMR element.
It is preferred that the at least a part of the insulation layers includes a GaN film. More preferably, the at least a part of the insulation layers includes an under layer of an AlN film, and a GaN film deposited on the AlN film.
Preferably, the AlN film is deposited by an electron cyclotron resonance sputtering (ECR), and the GaN film is deposited to have a strong orientation by a reactive sputtering using a high purity liquid target.
Thanks to thus deposited AlN/GaN film as the insulation layer of the thin-film magnetic head, lowering of the yield of the head due to ESD can be very effectively prevented.